frostbite-lcd

Show your CPU temperature on the pump-head LCD of a Dragos FrostBite (and other coolers whose Windows software is HJZN_PSR) — on Linux.

These coolers ship Windows-only software. Without it the display just sits at 00. This is a small daemon that reads the CPU temperature from hwmon and speaks the cooler's serial protocol, which was recovered by reverse engineering the vendor application. See docs/PROTOCOL.md for the full write-up.

No kernel module, no vendor blobs, no dependencies beyond Python 3.

Does this fit my cooler?

Run:

lsusb | grep 1f3a:0008

If you see a wch.cn/USB Serial device, you very likely have a compatible cooler. Confirmed working on:

Cooler	CPU	Distro
Dragos FrostBite 240	Ryzen 7 9800X3D	CachyOS (kernel 7.1)

Other rebrands of the same ODM design should work. If yours connects but shows the wrong number, see Different layout? below — and please open an issue so it can be supported out of the box.

Install

git clone https://github.com/hamer1818/frostbite-lcd
cd frostbite-lcd
sudo ./install.sh

The installer places the daemon in /usr/local/bin, installs a systemd unit, runs a dry-run check, and enables the service at boot.

Verify that the LCD agrees with your sensors:

sensors | grep -i tctl

Uninstall

sudo ./uninstall.sh

Usage

The service handles everything, but the daemon is usable directly:

frostbite-lcd --dry-run          # show what would be sent, write nothing
frostbite-lcd --interval 2       # update every 2 seconds
frostbite-lcd --temp-input /sys/class/hwmon/hwmon2/temp1_input
frostbite-lcd --device /dev/ttyACM1

Logs:

journalctl -u frostbite-lcd -f

How it works

hwmon (k10temp Tctl)  ->  frostbite-lcd  ->  /dev/ttyACM0  ->  pump-head LCD
                          1000000 baud, 8N1

Every second the daemon reads the CPU temperature and writes a six-byte frame:

74 01 02 31 00 02
^^          ^^
'|'         temperature, XOR 0x02   (0x31 = 49 = 51 ^ 2, i.e. 51 °C)

Both the serial device and the temperature source are resolved at runtime — the device by USB VID/PID, the sensor by chip name — because ttyACM numbering and hwmon indices are not stable across reboots. Unplugging the cooler and plugging it back in is handled; the daemon reconnects on its own.

Different layout?

If the daemon runs cleanly but the display is blank or wrong, your cooler may place the temperature in a different byte:

sudo ./tools/field-sweep.py

It sends a marker value through one field at a time. Watch the LCD and note which phase shows the marker, then open an issue with the result and the output of lsusb.

This is safe: the frames are the same shape the vendor software uses, and this serial link only drives the display. Pump and fans run off the motherboard headers and are unaffected — the worst case is a wrong number on screen.

Türkçe

Dragos FrostBite serisi sıvı soğutucuların pompa üzerindeki ekranı Windows'ta üreticinin yazılımıyla çalışıyor; Linux'ta karşılığı olmadığı için ekran 00 gösteriyor. Bu proje o yazılımın protokolünü tersine mühendislikle çözüp ekranın Linux'ta da çalışmasını sağlıyor.

Kurulum:

git clone https://github.com/hamer1818/frostbite-lcd
cd frostbite-lcd
sudo ./install.sh

Kurulum betiği servisi açılışta otomatik başlayacak şekilde ayarlar. Ekrandaki değeri sensors | grep -i tctl çıktısıyla karşılaştırarak doğrulayabilirsin.

Farklı bir modelde ekran yanlış değer gösteriyorsa sudo ./tools/field-sweep.py çalıştırıp hangi fazda doğru sayıyı gördüğünü issue olarak bildirebilirsin.

Contributing

Reports from other coolers are the most useful contribution — especially the lsusb line and your field-sweep.py result. Protocol findings for the unknown fields (bytes 2, 4 and 5) are very welcome too.

License

MIT. See LICENSE.

This project implements an interface for interoperability. It contains no vendor code and redistributes nothing from the original software.